Database Management

Supplement 1

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I. The Hierarchy of Data

• Database• File (Entity, Table)• Record (info for a specific entity, Row)• Field (Attribute, Column)• Data Types (only one type for a field)

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II. Relational Database• Relational Database Model: Most popular

database model. Data are stored in multiple tables. One table can be related to another table if they have a common field (usually primary key and foreign key).

• Primary key: one field or a combination of fields (column in a table) that uniquely identifies each record (row in a table). If there is no one single field that can be used to uniquely identify a record, a primary key is made of more than one field and called composite (concatenated) keys.

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What are Tasks for Database Administrator?

• Define data characteristics• Establish standards• Coordinate users and designers• Create, test and document programs• Data backup and recovery• Security controls

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What are standards important?

• Databases and tables were developed at different points in time by different people

• Consistent user interfaces• Standard reports• Data definition• Document changes in programs and databases.

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III. Microsoft Access

1. Basic definitions• Application generators: It enables you to

create applications without writing any programs. For Access database applications, you can create tables, queries, reports, forms, even macros without writing any programming commands.

• Seven objects of Access database: table, query, report, form, macro, VB module, and page.

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• Table: stores data for an entity (e.g., customer, order, loan, etc.) in rows (records) and columns (fields). A record includes all information about an instance of an entity. A field is a piece of information in a record.

• Query: answers questions by retrieving certain fields of certain records from one or more tables that satisfy a set of criteria.

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• Form: A form provides a user-friendly interface to enter, maintain and view records, and it is based on a table or a query.

• Report: It presents data from tables or queries in the way that you want.

• Page: It is a Web interface supported by Access and stored as a separate HTML file.

• Macro: a set of Access macro commands that automates tasks.

• Module: a program written in Visual Basic to automate tasks.

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2. Design a query

• QBE (Query By Example) vs. SQL: QBE is part of application generator. It enables you to generate queries without writing any programming commands– SQL is a query language for programming.– QBE is easier to use. SQL is more flexible

and powerful. Managers may prefer to use QBE.

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• To design a query, you need to answer four questions:– What output do you want to see? (fields to

show and how to sort)– What tables are involved?– What constraints are given? (criteria and

specified by developer or user) – How are the tables joined together?

(directly or through other tables)

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Query Exercise:

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IV. Database Design

What are goals for database design?

1. Capability of storing all pertinent data

2. Reduce redundant data

3. Keep the number of tables to a minimum

4. Normalize the tables so that to minimize update and deletion problems

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V. Database Design

What is normalization?

• Normalization is a design process that minimizes redundant data by separating data into interrelated tables.

• The normalization process can be defined by seven categories called normal forms in the order from the least restrictive to the most restrictive: Unnormal form, First normal form, Second normal form, Third normal form, Boyce-Codd normal form, Fourth normal form, and Fifth normal form.